Sound insulating device designed to be mounted in a tubular part, in particular a motor vehicle body part

ABSTRACT

A sound insulation device for mounting in a tubular part, in particular a motor vehicle bodywork part, the device comprising a partitioning insert, a cord of a composition that is thermally expandable so as to form a foam, said cord being fitted to the periphery of the insert, retaining means for holding the cord on the insert prior to expansion of the cord, and means for encouraging the cord to expand towards the inside wall of the tubular part, wherein the cord is formed by being extruded in rectilinear manner without any particular shaping, and wherein the cord retaining means are integrally molded with the partitioning insert and also serve to shape the extruded cord around the periphery of the partitioning insert.

[0001] The invention relates to a sound insulation device for mountingin a tubular part, in particular a motor vehicle bodywork part.

BACKGROUND OF THE INVENTION

[0002] Motor vehicle bodywork, in particular in the body proper,includes tubular parts such as pillars beside openings, side members, .. . , which constitute significant paths for propagating and deliveringnoise of various kinds into the vehicle cabin, thereby degradingpassenger comfort.

[0003] Providing sound insulation for such tubular parts thus poses aproblem, given that these parts are also of various shapes with varyingsections, and may themselves be built up by assembling together aplurality of parts.

[0004] In order to limit the propagation of such noise, vehiclemanufacturers have for a long time been closing off the inside sectionsof tubular parts by locally injecting a composition that can be causedto expand chemically so as to create a foam which comes into contactwith the inside wall of such a part and form at least one soundpartition. Foam is injected through a hole pierced in the part after thevehicle body has been painted. That solution generally givessatisfaction when the part, or the portion within the part, where thepartition is to be installed is generally in the form of a tube having aright section that is substantially circular and of diameter that is nottoo great. However, that solution presents the drawback of a hole beingpierced after the part has been painted, which constitutes an additionaloperation and which can run the risk of corrosion if the part is made ofmetal, and it requires the use of special equipment for injecting thefoam.

[0005] U.S. Pat. No. 5,642,914 discloses a sound insulation devicecomprising a thermally expandable material that is generally in the formof a flat ring fitted to the periphery of a partitioning insert. Thering is obtained by extrusion or by molding, thereby giving it inadvance the shape of the outline of the partitioning insert.

[0006] Document WO 01/83206 discloses a sound insulation device in whichthe thermally expandable material is molded on the periphery of apartitioning insert or is in the form of a strip which is bonded to theperiphery of said insert by adhesive or by means of staples.

OBJECTS AND SUMMARY OF THE INVENTION

[0007] An object of the invention is to devise a novel solution to theproblem of providing tubular parts with sound insulation, which solutionis suitable for being applied simply, and regardless of the shape of thesection of the part that needs to be insulated acoustically.

[0008] To this end, the invention provides a sound insulation device fora tubular part, in particular a motor vehicle bodywork part, the devicecomprising a partitioning insert, a cord of a composition that isthermally expandable so as to form a foam, said cord being fitted to theperiphery of the insert, retaining means for holding the cord on theinsert prior to expansion of the cord, and means for encouraging thecord to expand towards the inside wall of the tubular part, wherein thecord is formed by being extruded in rectilinear manner without anyparticular shaping, and wherein the cord retaining means are integrallymolded with the partitioning insert and also serve to shape the extrudedcord around the periphery of the partitioning insert.

[0009] Advantageously, the expandable cord is made of a vulcanizablesynthetic rubber mastic of the butyl, halogenated butyl, or nitriletype, of poylchloroprene, or of ethylene propylene diene monomer (EPDM),for example. It being understood that it is also possible to cause theexpansion or swelling ratio of the cord to vary on a case by case basisas a function of the space to be filled between the partitioning insertand the inside wall of the tubular part.

[0010] In an embodiment, the retaining means are constituted by hooks ofgutter shape which are disposed around at least a fraction of theperiphery of the partitioning insert so as to enable said insert to beunmolded without any problem of undercut.

[0011] Advantageously, the retaining hooks are disposed on oppositesides of the axis of the cord without being placed facing one another.

[0012] In general, the means for encouraging the cord to expand towardsthe inside wall of the tubular part are constituted by a peripheral wallwhich surrounds the partitioning insert, and the means for retaining thecord prior to expansion are situated outside the peripheral wall of theinsert.

[0013] In an embodiment, the insert presents overall a right section ofH-shape, with a central portion and the above-mentioned peripheral wallextending on either side of the central portion to form means thatencourage the cord to expand towards the inside wall of the tubularpart.

[0014] In another embodiment, the partitioning insert is constituted bytwo plates fixed one on the other and spaced apart from each other by aspacer-forming side wall that defines a peripheral groove suitable forreceiving an expandable cord, and leaks are provided through the sidewall to prevent the plates deforming while the cord is expanding.

[0015] A sound insulation device of the invention provides theparticular advantage of avoiding the need to shape the thermallyexpandable cord to match the shape of the outline of any specificpartitioning insert prior to fitting the cord thereto, and of enablingthe cord to be shaped and held without having recourse to additionalmeans, thereby facilitating the operations of mounting such a cord andbeing easily adaptable to partitioning inserts of arbitrary shape.

[0016] The invention also provides a tubular part, in particular a motorvehicle bodywork part, which tubular part includes a sound insulationdevice presenting all or some of the above-specified characteristics,with the cord being expanded thermally while the part is being painted.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Other advantages, characteristics, and details of the inventionappear from the additional description below given with reference to theaccompanying drawings themselves given purely by way of example, and inwhich:

[0018]FIG. 1 is a diagrammatic and fragmentary section view of a soundinsulation device for a tubular part, of the type described as priorart;

[0019]FIG. 2 is a perspective view for showing an embodiment of a soundinsulation device of the invention, the device comprising in particulara partitioning insert and a cord of expandable material;

[0020]FIG. 3 is a section view on line III-III of FIG. 2 for showing thesound insulation device prior to the cord being expanded;

[0021]FIG. 4 is a view similar to that of FIG. 3, after the cord hasbeen expanded;

[0022]FIG. 5 is a section view showing a variant fastening of thepositioning insert;

[0023]FIG. 6 is a section view showing another variant fastening for thepositioning insert; and

[0024]FIG. 7 is a section view showing another embodiment of a soundinsulation device of the invention.

MORE DETAILED DESCRIPTION

[0025] In the prior art mentioned in the introduction and as shown inFIG. 1, a tubular part T of motor vehicle bodywork is locally closed offon the inside by a plug of foam 3 which forms a sound insulationpartition to prevent noise propagating. A hole 5 is pierced through thepart T and a chemically expandable composition is injected through thehole 5 in order to create the foam plug 3.

[0026] An embodiment of the sound insulation device 10 of the inventionis shown in FIGS. 2 to 4. The insulation device 10 is for mountinginside a tubular part T and comprises at least one partitioning insert12, a flexible cord 14 of a composition suitable for expanding thermallyto form a foam, and retaining means 16 for holding the cord 14 to theperiphery of the insert 12 prior to expansion of the cord.

[0027] The partitioning insert 12 as shown is generally rectangular inoverall shape, it being understood that its shape depends on the shapeof the inside section presented by the tubular part T in the zone wherethe insert 12 is to be mounted.

[0028] The partitioning insert 12 presents a right section of H-shapewith a central portion 12 a bordered all around its periphery by aperipheral wall 12 b which extends on either side of the central portion12 a. This wall 12 b forms a barrier to prevent the cord 14 expandingtowards the inside of the insert 12, thereby encouraging it to expandtowards the inside wall of the tubular part T. The means 16 for holdingthe cord 14 are thus situated outside the peripheral wall 12 b.

[0029] The insert 12 also presents outside dimensions which are smallerthan the dimensions of the inside section of the tubular part T, firstlyto enable the cord 14 to be fitted thereto, and secondly to leave aperipheral gap (FIG. 3) which is subsequently filled by the foam (FIG.4) that results from the cord 14 expanding by a thermal effect.

[0030] The retaining means 16 for the cord 14 serve to hold the cord 14during operations of handling and mounting the insert, it beingunderstood that the cord is caused to expand thermally only subsequentlyduring the operation of painting the vehicle body, where a temperatureof about 150° C. to 200° C. suffices to cause it to expand. The cord 14is advantageously made by extrusion in the form of a substantiallyrectilinear rod without any special shaping, and the retaining means 16also serve to shape the cord 14 around the periphery of the partitioninginsert 12.

[0031] Furthermore, the retaining means 16 must not oppose expansion ofthe cord 14, i.e. the foam that results from said expansion must comeinto contact with the inside wall of the tubular part T all around theperiphery of the insert 12 like a sealing gasket.

[0032] In order to satisfy these conditions, the retaining means 16 areof a suitable shape which, in combination with the peripheral wall 12 bof the insert 12, encourages the cord 14 to expand towards the insidewall of the tubular part T. In general, the retaining means 16 aresituated on the outside of the wall 12 b. In the example shown in thedrawings, the retaining means 16 comprise at least hooks 18 a and 18 bin the form of gutters that are open towards the inside wall of thetubular part T so as to encourage the cord 14 to expand in thatdirection. Along one of the sides of the plate formed by the insert 12,the hooks 18 a and 18 b are disposed respectively on opposite sides ofthe cord 14 in alternating manner so that two hooks 18 a and 18 b do notface each other (FIG. 2). The hooks 18 a and 18 b may optionally bespaced apart regularly, or their disposition may vary as a function ofthe shape of the insert.

[0033] In addition, the retaining means 16 are not restricted to hooks18 a and 18 b of the type shown in the drawings, i.e. a single insert 12may have different retaining means, it being understood that a guttershape is preferred. For example, the retaining means 16 on at least oneside of the plate formed by the insert 12 may be constituted by a gutterwhich extends over substantially the entire length of said side.

[0034] In a preferred embodiment, the partitioning insert 12 is made ofa thermoplastic material such as a polyamide, for example, and theretaining means 16 are integrally molded with the insert 12. In otherwords, the hooks 18 a and 18 b are disposed in such a manner as toenable the insert 12 to be unmolded without any undercut problems.

[0035] The partitioning insert 12 must be of a shape that matches theshape of the tubular part in which it is to be mounted, which means thata variety of shapes are required, i.e. its shape is not restricted to aplate that is square or rectangular.

[0036] The cord 14 is advantageously made of a vulcanizable syntheticrubber of butyl, halogenated butyl, or nitrile type, of polychloropreneor of EPDM, for example, i.e. a material other than a thermoplastic. Inright section, the cord 14 may be of arbitrary shape, and will usuallybe square or circular.

[0037] In general, the expansion or swelling ratio of the cord 14 can becaused to vary as a function of the amount of space to be filled betweenthe insert 12 and the inside wall of the tubular part T. This space mayvary from one part to another with assembly tolerances that are criticalto a greater or lesser extent.

[0038] In order to cause the expansion or swelling ratio of the cord 14to vary, it suffices to add a swelling agent thereto in a quantity whichis a function of the desired expansion ratio. For example, it ispossible to select a large expansion ratio of the order of 1000% to1400% for a cord 14 having a diameter of about 5 millimeters (mm) to 7mm when the space to be filled between the insert 12 and the inside wallof the tubular part T is relatively large. In contrast, an expansionratio of about 100% to 500% may suffice for a cord having a diameter ofless than 4 mm when the space to be filled is small.

[0039] The partitioning insert 12 can be fastened to the inside of thetubular part T in various ways. When the insert 12 is made ofthermoplastic material, it can be fastened by means of at least oneresilient tab 20 forming a clip which is engaged in a hole 22 pierced inthe tubular part T. As shown in FIGS. 3 and 4, the resilient tab 20 issituated at the end of a lateral support arm 25 which locally extendsthe peripheral wall 12 b of the insert. Advantageously, this tab 20 andits support arm 24 are integrally molded with the insert 12. With thistype of fastening, the hole 22 pierced in the tubular part T is situatedon the same side as the source of noise.

[0040] In a variant shown in FIG. 5, the resilient fastening tab 20 canbe omitted by performing an operation of sticking the arm 25 to theinside of the tubular part T, thereby avoiding the need to pierce ahole.

[0041] In another variant shown in FIG. 6, the insert 12 is fixed bysoldering or welding a metal support bracket 25 which is connected tothe insert 12 by means of a plate 27 received in a rail defined by tworibs 29 projecting from one of the faces of the central portion 12 a ofthe insert 12.

[0042] It is also possible to envisage using a metal partitioning insertwith two techniques for implementing the retaining means. In the firsttechnique, the retaining means are formed directly on the periphery ofthe insert, thus requiring stamping and cutting operations to beperformed. In the second technique, the retaining means are made of aplastics material and are fitted to the periphery of the insert byadhesive, heat-sealing, clamping, snap-fastening, or the like.

[0043] In general, when the tubular part T is made by assemblingtogether a plurality of parts, the partitioning insert 12 can be fixedto at least one of the parts prior to the part being assembled to oneanother. However, when the tubular part T is a single piece, then thepartitioning insert 12 is mounted towards one of the ends thereof.

[0044] In another embodiment shown in FIG. 7, the partitioning insert 12is constituted by two pieces of thermoplastic material which areassembled to each other by adhesive or by snap-fastening. Moreprecisely, the first piece is a plate 31 with a side wall 33 projectingfrom one of its faces, the side wall being set back from the peripheraledge of the plate 31, and the second piece is a plate 32 fitted againstthe side wall 33. The two plates 31 and 32 assembled together in thisway have thickness of millimeter order, and between them then define aperipheral groove 35 suitable for receiving the cord 14. The two plates31 and 32 are fastened to each other by means of at least one clip 37,e.g. integrally molded with the plate 31 and penetrating in an opening39 made through the plate 32.

[0045] Leaks 40 are advantageously provided through the side wall 33 soas to ensure that swelling of the cord 14 does not lead to the plates 31and 32 being deformed.

[0046] These leaks 40 may be implemented in the form of holes 42 madethrough the side wall 33, or by a gap in said side wall. The leaks 40are preferably situated in rectilinear zones of the insert 12, i.e. inzones that are not critical.

[0047] Means for retaining the cord 14 by hooks of the kind describedfor the first embodiment are particularly well adapted to shaping andholding a cord that is relatively thick, i.e. that is quite stiff, for aspace to be filled that is relatively large. In contrast, when the spaceto be filled is smaller, it is possible to use a cord of smallerthickness and thus of greater flexibility. In which case, the retainingmeans can be of simpler design. By way of example, and as shown in FIG.7, the retaining means may be constituted merely by a peripheral rim 45surrounding the plate 31, possibly discontinuously.

[0048] Above it is assumed that the means for retaining the cord ofmastic are suitable for holding it to the periphery of the partitioninginsert without it being necessary to provide any fastening means.Nevertheless, it is also possible, optionally, to provide means forfastening the filler cord on the partitioning insert, e.g. by means ofadhesive.

What is claimed is:
 1. A sound insulation device for mounting in atubular part, in particular a motor vehicle bodywork part, the devicecomprising a partitioning insert, a cord of a composition that isthermally expandable so as to form a foam, said cord being fitted to theperiphery of the insert, retaining means for holding the cord on theinsert prior to expansion of the cord, and means for encouraging thecord to expand towards the inside wall of the tubular part, wherein thecord is formed by being extruded in rectilinear manner without anyparticular shaping, and wherein the cord retaining means are integrallymolded with the partitioning insert and also serve to shape the extrudedcord around the periphery of the partitioning insert.
 2. A deviceaccording to claim 1, wherein the expandable cord is made of avulcanizable synthetic rubber mastic of the butyl, halogenated butyl, ornitrile type, of poylchloroprene, or of EPDM, for example.
 3. A deviceaccording to claim 1, wherein the expandable cord presents a variableswelling ratio which is selected as a function of the space to be filledbetween the insert and the inside wall of the tubular part.
 4. A deviceaccording to claim 3, wherein the swelling ratio of the expandable cordis about 1000% to 1400%, and wherein the diameter of the cord is about 5mm to 7 mm.
 5. A device according to claim 3, wherein the swelling ratioof the expandable cord is about 100% to 500%, and wherein the diameterof the cord is less than 4 mm.
 6. A device according to claim 1, whereinthe retaining means comprise at least hooks of gutter shape and disposedon at least a fraction of the outline of the partitioning insert in sucha manner as to enable said insert to be unmolded without any undercutproblem.
 7. A device according to claim 6, wherein the retaining hooksare disposed on either side of the axis of the cord without facing oneanother.
 8. A device according to claim 1, wherein the means forencouraging the cord to expand towards the inside wall of the tubularpart are constituted by a peripheral wall surrounding the partitioninginsert, and wherein the retaining means for retaining the cord prior toexpansion thereof are situated at the outside of the peripheral wall ofthe insert.
 9. A device according to claim 8, wherein the insert isgenerally H-shaped in right section, with a central portion and theperipheral wall which extends on either side of the central portion toform the means which encourage the cord to expand towards the insidewall of the tubular part.
 10. A device according to claim 1, wherein thepartitioning insert is constituted by two plates fixed to each other andfaced apart from each other by a spacer-forming side wall defining aperipheral groove suitable for receiving an expandable cord, and whereinleaks are provided through the side wall to prevent the plates deformingwhile the cord is expanding.
 11. A device according to claim 1, whereinthe insert is made of a thermoplastic material such as polyamide.
 12. Adevice according to claim 1, wherein the insert is fixed to the tubularpart by means of at least one flexible tab which is engaged in a holepierced in the tubular part.
 13. A device according to claim 12, whereinthe flexible fixing tab is at the end of a support arm secured to theinsert.
 14. A device according to claim 12, wherein the fixing tab andthe support arm are integrally molded with the insert.
 15. A deviceaccording to claim 1, wherein the insert is fastened to the tubular partby adhesive or by soldering or by welding.
 16. A tubular part, inparticular a motor vehicle bodywork part, the tubular part including asound insulation device as defined by claim
 1. 17. A tubular partaccording to claim 16, wherein the cord is expanded thermally while thepart is being painted.